For detecting movements consequently presences of objects and/or living beings in a limited area, in particular of an indoor area, many different approaches (e.g. methods, systems etc.) exist, but all of them have limitations.
Talking in the following about “movement detection” means in the context of the application a “movement and consequently presence detection”. The reason for this is: When e.g. only the movement of a human or animal inside a room is detected (movement detection; “only” means there is e.g. no camera showing whether the movement comes originally from the human or animal), then the statement which can be made only for sure is that somebody or something is in the room (presence detection; but for the decision, whether the detected movement goes back to a human or animal, more especially sensor-related information is necessary).
A limited area besides the mentioned indoor area but outside of a building is for example a radio range, whereby the limitation is given by the radio coverage.
A first obviously known approach for movement detection is based on a simple motion detector (i.e. Passive Infra-Red sensor—PIR sensor). Such a simple motion detector will be a cheap and simple way to detect if a person is in a room as a typical indoor area. However, in order to cover a whole apartment as another larger indoor area, one sensor per each room has to be set up, because PIR sensors cannot see through walls. This will require setting up data communication and power for each of the sensors, as well as looking for suitable positions for said sensors.
A very innovative alternative to the “simple motion detector”-based scenario is the use of gas sensors built into an apparatus to detect the presence of people. The main disadvantage of such an approach is that it will take several minutes to detect such a presence, which is undesirable when controlling the lighting of the apartment. It should be mentioned that at the moment this approach cannot be found in any commercial devices.
Yet another approach to the “simple motion detector”-based scenario is to detect the use of equipment inside the apartment, for example switching on and off televisions, tablets or cooking appliances. While this would certainly be a positive indication of the presence of somebody in the apartment, this approach also has an undesirable delay especially if no equipment is used, which would not allow it to be used for applications such as turning on lighting.
Even another approach which would trigger home automation equipment in a similar fashion to the “simple motion detector”-based scenario, and one that can already be found in the market, is to program beforehand the time in which the apartment will be occupied, so that the thermostat and lighting may be turned on in advance. Unfortunately, people don't always go in and out of the apartment the exact same minute, leading to energy waste when the programmed time has arrived but the people haven't.
Lastly, if people were forced to always carry a device with them (for example a smartphone), the device's sensors and wireless communication may be used for presence detection. However, this would force people to always carry such devices with them, having them turned on at all time and charged. This presents an important limitation when detecting children and pets inside the apartment.
Other approaches may exist. But none of these fulfill the following requirements raised out of the above reflection of the different approaches:                Fast acting,        Covering the limited area (e.g. a radio range), in particular the whole apartment,        People carrying no devices        Off-the-shelf hardware and        Single-Sensor.        